Stencil recording apparatus

ABSTRACT

The device of this invention uses electrostatic recording to apply original titles, legends, or other indicia to discrete record receivers. The system includes changeable stencils which, for the purposes of this description, are constructed as counters. The desired information is set up, a voltage is applied between the stencil and an electrode behind a record receiver, ionized pigmented particles are attracted through the stencils to the record receiver, and the record receiver is moved to a fixing station. By rendering the individual items of information changeable, any desired information within the range of the apparatus can be applied to an appropriate record receiver.

United States Patent Greenly [541 STENCIL RECORDING APPARATUS Robert B. Greenly, Santa Clara, Calif.

Singer-General Precision, Inc., Binghamton, NY.

[22] Filed: Dec.3l, 1968 [21] Appl.No.: 788,150

[72] Inventor:

[73] Assignee:

3,408,984 11/1968 Pullins ....101/1 19 X 2,152,077 3/1939 Meston et a1. l01/D1G. 13

2,586,047 2/1952 l'luebner ..101/116 2,618,551 11/1952 Walkup 95/1.9 2,836,147 5/1958 McComb.. 118/620 2,919,170 12/1959 Epstein ....346/74 3,017,234 1/1962 Trimble et a1. ..346/74 1 Feb. 1,1972

Primary ExaminerClyde 1. Coughenour Attorney-Francis L. Masselle, William Grobman and Andrew G. Pullos [5 7] ABSTRACT The device of this invention uses electrostatic recording to apply original titles, legends, or other indicia to discrete record receivers. The system includes changeable stencils which, for the purposes of this description, are constructed as counters. The desired information is set up, a voltage is applied between the stencil and an electrode behind a record receiver, ionized pigmented particles are attracted through the stencils to the record receiver, and the record receiver is moved to a fixing station. By rendering the individual items of information changeable, any desired information within the range of the apparatus can be applied to an appropriate record receiver.

4 Claims, 6 Drawing Figures PATENTEDFEH 1 872 3,638,566

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IN VEN TOR. ROBERT B. GREENLY STENCIL RECORDING APPARATUS This invention relates to machines for applying information to record receivers, and, more particularly, for applying selected information to record receivers by means of electrostatic recording.

Xerography is a valuable boon to modem-day commerce as an office duplicating device. Most present-day xerographic equipment is designed to create an electrostatic image of an already existing document. However, the same principles of recording can be used initially to print desired information. For example, a series of articles are often to be numbered sequentially. One form of device for accomplishing this can include electrostatic printing. Normally sequential numbering apparatus comprises three major portions. They are: (l numbered print wheels; (2) means for stepping the print wheels to a new position for each item to be printed; and (3) means for applying a pigment to the print wheels. The recording apparatus of this invention comprises the same major components. However, the print wheels are specially formed screen stencils. The means for changing the position of the print wheels can be of standard construction, and the means for applying the pigment to the print wheels also includes the means for making the appropriate impression upon the record receiver.

In general, the print wheels comprise a plurality of counting wheels which are formed of an appropriate conductive screen material in which the numbers or letters to be printed are formed by areas of the screen which have been left open. A pigment in the form of a powder is continually applied to the interior of the print wheels, but an electrical field potential is established to prevent the pigment from penetrating the open screen of the character. When a particular character is to be printed, the potential is varied and the pigment is deposited upon the record receiver. Fixing or other steps can be taken to make the record a permanent one.

In the past sequential numbering apparatus often printed upon intermittently moving surfaces. In high-speed equipment during the short interval of time that one portion of a record receiver is replaced by another, the printing counter must be stepped. Thus, during an interval of time there are two motions taking place-the number on the counter is moving while the record receiver is also moving. Since printing is ordinarily accomplished by a third movement, that of bringing the printing counter together with the record receiver, either directly or through a ribbon, prior art printing equipment was often slow or resulted in smeared printing. One of the advantages of the apparatus of this invention is that the actual printing is rapid, and takes place in a very short interval of time and does not occur until an electrical signal is applied. No large masses are moved, and the printing signal can be applied when all of the elements involved have come completely to rest.

It is an object of this invention to provide a new and improved printing apparatus.

It is another object of this invention to provide a new and improved printing apparatus which utilizes electrostatic recording for forming an image.

It is a further object of this invention to provide a new and improved xerographic sequential printer in which an electrostatic medium is used to imprint characters upon a record receiver.

Other objects and advantages of this invention will become apparent as the following description proceeds, which descrip tion should be considered together with the accompanying drawings in which:

FIGS. 1 and 2 are schematic showings of a simplified portion of the apparatus of this invention to illustrate the principles involved;

FIG. 3 is an electrical schematic circuit diagram which illustrates the implementation of the apparatus of this invention;

FIG. 4 is an elevational view, partially in section, of one form of apparatus in accordance with this invention; and

FIGS. 5 and 6 are enlarged detailed views of the numbering apparatus of this invention.

Referring now to the drawings in detail and more particularly to FIGS. 1 and 2, the reference character 11 designates a screen mesh in which the openings have been filled by a suita-- ble material except for an area 19 which defines a character to be printed. A record receiver 12 is shown lying between the stencil 11 and an electrode 13. The electrode 13 is connected to one side of a source of electricity such as the battery 14 shown. The other side of the battery 14 is connected to a stationary contact 16 of a two-position switch 15, the other stationary contact 17 of which is grounded. The moveable contact of the switch 15 is connected to the screen 11. In addition, particles of powdered pigment 18 are shown adjacent one side of the stencil 11.

In operation, as shown in FIG. 1, the switch 15 has closed a circuit through the battery 14 applying a positive potential to the electrode 13 and a negative potential to the stencil 11. The pigment particles 18 have been previously ionized by any suitable means so that they have acquired a negative charge. The repulsion between the charges on the stencil 11 and the pigment l8 effectively prevents the pigment 18 from penetrating the open spaces in the stencil 11 and depositing upon the record receiver 12. However, should the switch 15 be moved to its second position so that thescreen 11 is grounded, the potential of the screen 11 no longer repels the pigmented particles l8, and they are attracted to the record receiver 12. Since most of the screen 11 has been filled in by a suitable material such as that used for preparing silk screens, the pigment particles 18 pass through only the open portions of the stencil 1 1. These open portions ofthe stencil are formed in the shape of the character to be printed, in this case the numeral 3. If the record receiver 12 were in direct contact with the stencil 11, then the individual wires of the mesh material would be seen on the record receiver as unprinted lines. However, by providing a space between the stencil 11 and the record receiver 12, room is permitted for the particles passing through the mesh in the stencil 11 to diffuse slightly, and the printed character appears as a solid number.

For purposes of the apparatus of this invention, the use of a manually operated switch 15 is entirely too slow. In addition, the operation should be automatic and should occur without the need of an outside operator. A suitable automatic switching device is shown in FIG. 3. In this figure the electrode 13 is shown as a flat plate backing up the record receiver 12, and the stencil 11 is shown as a screen or grid. The plate 13 is connected to one side of the battery 14, and the other side of the battery 14 is connected through a second battery 26 and a resistor 27 to the stencil 11. Connected across the circuit is a gas-filled tube 21 having an anode 22, a cathode 23 and a control electrode 24. The anode 22 is connected to the stencil l1 and the cathode 23 is connected to the negative side of the battery 14. The secondary of a transformer 25 is connected between the control electrode 24 and the cathode 23. One side of the primary of the transformer 25 is grounded, and the other side is connected through a capacitor 36 to the anode of an SCR 31, whose cathode is connected through a switch 37 to ground. The control electrode of the SCR 31 is connected through a switch 32 to the slide contact of a potentiometer 33. The potentiometer 33 is connected across a battery 34, the positive terminal of which is connected through a resistor 35 to the anode of the SCR 31.

As shown, a negative potential is ordinarily applied to the stencil I1, and a positive potential is applied to the electrode 31. Since the particles of the powder 18 are ionized with a negative charge, they are repelled by the electrical field around the stencil 11 and do not pass therethrough. However, when the switch 32 is closed (this is symbolic for the application of an electrical signal), a signal is applied to the control electrode of the SCR 31, causing the SCR to fire and discharge the capacitor 36. A sharp pulse is applied to the primary of the transfonner 25 applying another sharp pulse between the control electrode 24 and cathode 23 of the gas tube 21. The gas tube 21 (also known as a gas tilled arc tube) fires and short-circuits the screen 11. This drops the potential of the screen 11 virtually to ground, and no negative electrical field remains to repel the particles 18. The positive field created by the electrode 13 attracts the particles 18 which pass through the open portions of the stencil 11 and are deposited on the record receiver 12 in a pattern which duplicates the character of the screen 1 1.

As indicated above, the switch 32 is merely a symbolic showing of a source of electrical signals. As one example of such a source, a digital computer may be used to control the entire printing operation.

The overall apparatus is shown in FIG. 4. This comprises a printing station 51 which includes printing wheels 52, driving gears 53 and a transfer mechanism 54. A charged plate 55 is positioned opposite that part of the station through which the record receivers pass. A tube 56 is connected to a blower 57 driven by an electric motor 65 for moving particles of pigment 18 from a bin 61 and charged plastic beads from a bin 66 to the printing station 51. A vibrator 62 is mounted on the bin 61 which includes a door through which the particles 18 may pass into a funnel 59. A gauze filter 58 provides a means for drawing air into the tube 56 without drawing in other particles. That pigment which is not used is blown by the blower 57 through a return tube 64 into a reserve storage bin 66. The storage bin 66 includes an opening operating means 67.

In operation the print wheels 52 are electrically set up to desired characters which are to be printed on a record receiver. A record receiver is then positioned at the print station 51 beneath the wheels 52. The print wheels 52 could readily be constructed about the outside of the tube 56 with an opening in the tube 56 at the bottom exposing the inside of the print wheels to the interior of the tube 56. Thus, as the blower 57 draws the pigment particles 18 and the beads through the funnel 59 and past the print station 51, the electrostatic charge on the print wheels 52 can be removed to cause the charged pigment particles to pass through the wheels and onto the record receiver stationed there. The beads are recirculated by the pump 57 and blown through the tube 64 to the excess storage bin 66. Generally, the plastic heads will be supplied from the bin and the material 18 will be supplied from the bin 61 with the vibrator 62 providing a ready means for shaking the material out of the bin 61. As the beads move, they acquire electrical charges due to friction and then transfer the negative charges to the particles 18 as the particles l8 and beads pass through the funnel 59, the filter 58 and the tube 56. Or, instead of the plastic beads to maintain this charge, the entire system of the tube 56 can be so charged.

FIGS. and 6 illustrate one form in which the print wheels can be constructed. As shown in FIG. 5, the tube 56 has mounted on the outside thereof a set of four number wheels 71 having a series of numbers 72 thereon. The print wheels 71 are constructed in a manner similar to the stencils shown in FIG. 1 with open mesh forming the numbers. The print wheels 71 are readily rotatable around the outside of the tube 56 by means of the gears 73. The gears 72 are so arranged so only one gear is driven from an external source, that gear to the far left. As that gear rotates, it rotates the left gear in the transfer mechanism 74 which is better seen in FIG. 6. When the gear 74 has driven the left gear 73 through a complete revolution, a single transfer tooth 73, which is mounted on that gear between positions 9 and 0, catches the middle gear 74 and drives it through one number position. Thus, each time the lowest order gear 73 makes a complete revolution, it drives the next higher order gear 73 through one-tenth of a revolution, or a single character position. In this manner, a stepping counter which sequences is used to automatically number successive record receivers with the next higher number. As each gear 73 rotates, it, in turn, drives a print wheel 71. As shown in FIG. 6, an opening 76 penetrates the wall of the tube 56 so that the pigment particles 18 flowing through the tube 56 can be drawn through the opening 76 and through the open spaces which define the character immediately beneath the opening 76 to be applied to the record receiver 12 to form a a number thereon.

The apparatus disclosed herein rs one form which a sequential printer can take. The pigments such as the particles 18 can be of any desirable type. Because of this, no fixing station has been shown, but it must be realized that when a heat settable plastic material is used as the pigment 18. a fixing station which applies heat to the printed record receiver can be used to form a permanent record. Other types of pigments may require different forms of fixing or no fixing at all. It is realized that the above description may indicate to those skilled in the art additional ways in which this invention may be used and, it is, therefore, intended that this invention be limited only by the scope of the appended claims.

What is claimed is:

1. Printing apparatus comprising a printing station, a pigment supply source, means for moving pigment from said supply source to said printing station, and means for recovering surplus pigment from said printing station and returning said surplus pigment to said source; said printing station com prising a plurality of controllable character wheels, each of said character wheels comprising a hollow cylinder with an outer skin having porous areas disposed about the periphery of said cylinder to define a plurality of printable characters disposed about said periphery, an electrode at said printing station facing said wheels but spaced therefrom to define a record receiver space, means for selectively positioning said wheels so that only selected characters face said record receiver, means for selectively applying an electrical field across said record receiver space to cause said pigment to pass through said porous characters onto said record receiver, a granular carrier for said pigment, means for injecting said carrier grains into said air stream, said carrier being formed of a material which acquires an electrical charge due to friction, the charge developed by said granular carrier being transferred to said pigment by contact therewith, means for recirculating said granular carrier, said recirculating means including a magazine for said carrier including said means for injecting said carrier into the airstream, and tubular guiding means for guiding said carrier back to said magazine, said tubular guide means passing through the interior of said character wheel.

2. The apparatus defined in claim 1 wherein said means for applying an electrical field comprises a source of electrical energy, means for connecting one side of said source to said electrode, means for connecting the other side of said source to said character wheels to establish an electrical field between said electrode and said wheels, and means for periodically removing said field.

3. The apparatus defined in claim 2 wherein said means for periodically removing said field comprises means for periodically interrupting the application of said potential to said electrode and said wheel.

4. The apparatus defined in claim 3 wherein said interrupt ing means comprises means for temporarily short-circuiting said source of electrical energy.

* I i i 

1. Printing apparatus comprising a printing station, a pigment supply source, means for moving pigment from said supply source to said printing station, and means for recovering surplus pigment from said printing station and returning said surplus pigment to said source; said printing station comprising a plurality of controllable character wheels, each of said character wheels comprising a hollow cylinder with an outer skin having porous areas disposed about the periphery of said cylinder to define a plurality of printable characters disposed about said periphery, an electrode at said printing station facing said wheels but spaced therefrom to define a record receiver space, means for selectively positioning said wheels so that only selected characters face said record receiver, means for selectively applying an electrical field across said Record receiver space to cause said pigment to pass through said porous characters onto said record receiver, a granular carrier for said pigment, means for injecting said carrier grains into said air stream, said carrier being formed of a material which acquires an electrical charge due to friction, the charge developed by said granular carrier being transferred to said pigment by contact therewith, means for recirculating said granular carrier, said recirculating means including a magazine for said carrier including said means for injecting said carrier into the airstream, and tubular guiding means for guiding said carrier back to said magazine, said tubular guide means passing through the interior of said character wheel.
 2. The apparatus defined in claim 1 wherein said means for applying an electrical field comprises a source of electrical energy, means for connecting one side of said source to said electrode, means for connecting the other side of said source to said character wheels to establish an electrical field between said electrode and said wheels, and means for periodically removing said field.
 3. The apparatus defined in claim 2 wherein said means for periodically removing said field comprises means for periodically interrupting the application of said potential to said electrode and said wheel.
 4. The apparatus defined in claim 3 wherein said interrupting means comprises means for temporarily short-circuiting said source of electrical energy. 